A common obstacle faced by pipe manufacturers is the monitoring of the uniformity of pipe wall thickness during the manufacturing process. Ductile iron pipe is centrifugally cast by pouring molten iron down a U-shaped trough into an externally water-cooled rotating steel mold. The casting machine traverses the length of the trough as molten iron fills the bell cavity and body of the mold. This casting method is known as the deLavaud process. When the pipe is extracted from the mold, its temperature is approximately 1000° F. Due to the brittle nature of the pipe at this point in the manufacturing process, it must be annealed. In the annealing cycle, the pipe is placed in a furnace, where it is heated to temperatures of approximately 1700° F.
During the manufacturing process, particular attention is paid to the uniformity of thickness of the pipe wall after casting. A common technique used to measure pipe wall thickness has been the time-of-flight method. This technique uses a couplant applied to the surface of the pipe and a transducer to send an ultrasonic wave through the couplant into the outer surface of the pipe wall. The transducer then receives the ultrasonic wave after it has reflected from the inner surface of the pipe wall and passed through a couplant. Thickness is ultimately determined by measuring the time between the sending of the ultrasonic pulse and receipt of the reflected pulse.
Although this technique can be useful in measuring pipe wall thickness when the pipe is at a relatively low temperature, high-temperature pipes are not typically measured using the time-of-flight method due to the inability of typical coupling mediums such as oil, water, and glycerin to withstand the high surface temperatures of the pipe walls. Thus, a pipe exiting the casting process at a temperature of approximately 1000° F. or higher must first be cooled before it can be subjected to a time-of-flight measurement. Because this technique requires cooling in order to measure pipe thickness in-process, there is an inherent delay in providing feedback to the casting system. Further, cooling the pipe for thickness measurement would require greater energy to reheat the pipe during the annealing process. What are needed are systems and methods for providing in-process thickness data for use in the casting process.